This application is related to and claims priority from Japanese Patent Applications No. Hei. 11-8146 filed on Jan. 14, 1999, No. Hei. 11-20519 filed on Jan. 28, 1999, and No. Hei. 11-148811 filed on May 27, 1999, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a heat exchanger formed by only using plural plates for defining inside fluid passages through which an inside fluid flows. The heat exchanger is suitably applied to a refrigerant evaporator for a vehicle air conditioner.
2. Description of Related Art
In a conventional refrigerant evaporator for a vehicle air conditioner, a corrugated fin having louvers for increasing heat-transmitting area is disposed between adjacent flat tubes each of which is formed into a hollow shape by connecting a pair of plates facing each other. In this case, when a flow rate of air passing through the corrugated fines becomes high, over-pressure loss may be caused. Therefore, in the conventional refrigerant evaporator, the flow rate of air passing through the corrugated fins is generally set to be lower. Thus, for improving heat-transmitting performance on an air side in the conventional refrigerant evaporator, top-end effect of the louvers is used so that a boundary layer is made thinner. In the recent years, because the louvers is made finer until a processing limit, processing steps become difficult. Further, because the corrugated fins are assembled between adjacent flat tubes, assembling performance of the refrigerant evaporator is deteriorated. That is, since a conventional heat exchanger needs corrugated fins, it is difficult to reduce the manufacturing cost and the size of the heat exchanger.
In view of the foregoing problems, it is an object of the present invention to provide a heat exchanger which is formed by only using plural heat-exchanging plates defining an inside fluid passage without using a fin member such as a corrugated fin, while having a sufficient heat-transmitting performance.
It is an another object of the present invention to provide a heat exchanger formed by only using plural heat-exchanging plates defining plural inside fluid passages, which readily detects an inside fluid leakage between the inside fluid passages.
It is a further another object of the present invention to provide a refrigerant evaporator formed by only using plural heat-exchanging plates defining an inside fluid passages, which prevents condensed water from scattering on a downstream air side thereof.
It is a further another object of the present invention to provide a heat exchanger formed by only using plural heat-exchanging plates defining an inside fluid passage, which has a reduced small size and is manufactured in low cost by thinning the heat-exchanging plates.
According to the present invention, a heat exchanger for performing a heat exchange between an inside fluid and an outside fluid includes plural pairs of heat-exchanging plates each having a plurality of projection ribs. Each pair of the heat-exchanging plates face each other in such a manner that, the projection ribs protrude outwardly to form therein an inside fluid passage through which the inside fluid flows, and to form an outside fluid passage through which the outside fluid flows between adjacent pairs of the heat-exchanging plates. Further, the projection ribs protrude from flat surfaces of the heat-exchanging plates to the outside fluid passage to disturb a flow of the outside fluid, the projection ribs are provided in each of the heat-exchanging plates to have a protrusion pitch (P1) between adjacent two, and the protrusion pitch is in a range of 2-20 mm. Thus, even in the heat exchanger without a fin member, a straight line flow of outside fluid is disturbed by the protrusion outer portions of the projection ribs, and a necessary heat-exchanging effect is obtained. Further, because the heat exchanger is formed only by using the heat-exchanging plates, the heat exchanger is manufactured in low cost, and a size of the heat exchanger is reduced. Further, because the protrusion pitch is set in the range of 2-20 mm, heat-exchanging performance of the heat exchanger is effectively improved.
Preferably, adjacent pairs of the heat-exchanging plates are provided to have a passage pitch (P2) which is a distance between the inside fluid passages of the adjacent pairs of the heat-exchanging plates, and the passage pitch is in a range of 1.4-3.9 mm. Therefore, the heat-exchanging performance of the heat exchanger is improved while the pressure loss in the outside fluid passage is restricted in a predetermined range.
More preferably, the protrusion pitch is set in a range of 10-20 mm, and the passage pitch is set in a range of 1.4-2.3 mm. Therefore, the heat-exchanging performance is further effectively improved.
Further, adjacent pairs of the heat-exchanging plates have a clearance therebetween to form the outside fluid passage, and the clearance is in a range of 0.7-1.95 mm. The inside fluid passages are provided inside the projection ribs by connecting each pair of the heat-exchanging plates. On the other hand, each of the heat-exchanging plates has a plate thickness, and the plate thickness is in a range of 0.1-0.35 mm. Thus, the heat-exchanging plate is made thinner, the weight of the heat exchanger is reduced, and heat-exchanging performance per volume is improved.
Preferably, the projection ribs extend in an up-down direction approximately perpendicular to a flow direction of the outside fluid. Therefore, when the heat exchanger is used as an evaporator, condensed water generated on protrusion top surfaces of the projection ribs is smoothly discharged downwardly. Thus, draining performance of condensed water is improved in the evaporator, and air-flow resistance is prevented from increasing due to condensed water on the protrusion top surfaces of the projection ribs.
Further, the inside fluid passages of the heat exchanger are partitioned into a first inside fluid passage group and a second inside fluid passage group in the flow direction of the outside fluid, each pair of the heat exchanging plates have an inner leakage-detecting projection rib between the first inside fluid passage group and the second inside fluid passage group in the flow direction of the outside fluid, the inner leakage-detecting projection rib extends along the projection ribs, and the inner leakage-detecting projection rib has therein an inner leakage-detecting passage opened to an outside. Therefore, when an inner leakage is generated in the heat exchanger so that the first inside fluid passage group and the second inside fluid passage group communicate with each other, the inside fluid is discharged to an outside from the inner leakage-detecting passage. Thus, an inner leakage is simply and accurately detected.
Preferably, each of the heat-exchanging plates is composed of an aluminum core layer, a brazing layer clad on one surface of the aluminum core layer, and a sacrifice corrosion layer clad on the other surface of the aluminum core layer. Further, each pair of the heat-exchanging plates are connected by bonding the flat surfaces to each other through brazing using the brazing layer. Thus, the heat-exchanging plates becomes thinner, and are manufactured in low cost.
More preferably, the inside fluid passages are partitioned into a first inside fluid passage group and a second inside fluid passage group in the flow direction of the outside fluid, the heat-exchanging plates have tank portions at an end side in an extending direction of the projection ribs, the tank portions protrude from the flat surfaces to form communication holes, the tank portions are partitioned into a first tank member and a second tank member at an upstream side of the first tank member in the flow direction of the outside fluid. The first tank member communicates with the first inside fluid passage group and the second tank member communicates with the second inside fluid passage group. Further, the first tank member has a dimension in the up-down direction smaller than that of the second tank member. Thus, within the heat exchanger, a downstream flow area is enlarged as compared with an upstream flow area in the flow direction of the outside fluid. Accordingly, when the heat exchanger is used as a refrigerant evaporator so that air passing through the evaporator is cooled, it can effectively prevent condensed water from scattering to a downstream air side from a downstream air end of the evaporator.